Water-based ink for ink-jet recording, ink cartridge, and ink-jet recording method

ABSTRACT

A water-based ink for ink-jet recording includes: a pigment; water; at least one of a water-soluble resin having a minimum film-forming temperature of not more than 80° C. and a water-dispersible resin having a minimum film-forming temperature of not more than 80° C.; and a micelle-forming compound having an alkyl group and an oxyethylene chain.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2015-073802 filed on Mar. 31, 2015, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a water-based ink for ink-jetrecording, an ink cartridge, and an ink-jet recording method.

Description of the Related Art

As inks used for ink-jet recording, water-based pigment inks having apigment and water have been suggested (Japanese Patent Applicationlaid-open No. 2004-231711). The ink-jet recording using the water-basedpigment ink, however, has a problem in which the fixation performance toglossy paper is not good.

SUMMARY OF THE INVENTION

Ink-jet recording apparatuses have been widely used in offices,companies, and the like in recent years, and there has been growing thedemand for a recording matter recorded by the ink-jet recordingapparatus which is less likely to get dirty even if being rubbed. Underthese circumstances, the water-based pigment ink is required to have agood fixation performance to glossy paper.

In view of the above, an object of the present teaching is to provide awater-based ink for ink-jet recording which has a good fixationperformance to glossy paper.

According to a first aspect of the present teaching, there is provided awater-based ink for ink-jet recording including: a pigment; water; atleast one of a water-soluble resin having a minimum film-formingtemperature of not more than 80° C. and a water-dispersible resin havinga minimum film-forming temperature of not more than 80° C.; and amicelle-forming compound having an alkyl group and an oxyethylene chain.

According to a second aspect of the present teaching, there is providedan ink cartridge which includes the water-based ink for ink-jetrecording as defined in the first aspect.

According to a third aspect of the present teaching, there is providedan ink-jet recording method including discharging a water-based ink forink-jet recording on a glossy paper in accordance with an ink-jet systemto perform recording, wherein the water-based ink for ink-jet recordingis the water-based ink for ink-jet recording as defined in the firstaspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C each illustrate an exemplary assumed mechanism about theimprovement of fixation performance to glossy paper according to thepresent teaching.

FIGS. 2A to 2C each illustrate another exemplary assumed mechanism aboutthe improvement of fixation performance to glossy paper according to thepresent teaching.

FIG. 3 is a schematic perspective view of an exemplary construction ofan ink-jet recording apparatus according to the present teaching.

DESCRIPTION OF THE EMBODIMENTS

It is preferred that a recording medium, for which recording isperformed by using a water-based ink for ink-jet recording of thepresent teaching (hereinafter also referred to as “water-based ink” or“ink” in some cases), be glossy paper. The glossy paper means, forexample, recording paper in which at least not less than one coatinglayer(s) is/are formed on its recording surface. The coating layer(s)is/are made of silica particles, alumina particles, or the like.Examples of the glossy paper include photo glossy paper “BP61G” “BP71G”and “BP71GA4” manufactured by BROTHER KOGYO KABUSHIKI KAISHA; ink-jetpaper “Kassai” Photo-finish Pro manufactured by FUJI FILM CORPORATION;and highest grade glossy paper “PWRA4-20” manufactured by KODAK JAPANLTD. The average of diameter sizes of typical voids of the coating layerof the glossy paper is in a range of about 10 nm to about 50 nm.

An explanation will be made about the water-based ink of the presentteaching. The water-based ink of the present teaching contains a pigmentand water.

The pigment is not particularly limited and includes, for example,carbon black, inorganic pigment, and organic pigment. The carbon blackincludes, for example, furnace black, lamp black, acetylene black, andchannel black. The inorganic pigment includes, for example, titaniumoxide, iron oxide-based inorganic pigment, and carbon black-basedinorganic pigment. The organic pigment includes, for example,azo-pigments such as azo lake, insoluble azo-pigment, condensedazo-pigment, chelate azo-pigment and the like; polycyclic pigments suchas phthalocyanine pigment, perylene and perynon pigments, anthraquinonepigment, quinacridone pigment, dioxadine pigment, thioindigo pigment,isoindolinone pigment, quinophthalone pigment and the like; dye lakepigments such as basic dye type lake pigment, acid dye type lake pigmentand the like; nitro pigments; nitroso pigments; and aniline blackdaylight fluorescent pigment. Other pigments are also usable providedthat the pigments are dispersible in the water phase. The pigments areexemplified, for example, by C. I. Pigment Blacks 1, 6, and 7; C. I.Pigment Yellows 1, 2, 3, 12, 13, 14, 15, 16, 17, 55, 73, 74, 75, 78, 83,93, 94, 95, 97, 98, 114, 128, 129, 138, 150, 151, 154, 180, 185, and194; C. I. Pigment Oranges 31 and 43; C. I. Pigment Reds 2, 3, 5, 6, 7,12, 15, 16, 48, 48:1, 53:1, 57, 57:1, 112, 122, 123, 139, 144, 146, 149,150, 166, 168, 175, 176, 177, 178, 184, 185, 190, 202, 221, 222, 224,and 238; C. I. Pigment Violets 19 and 196; C. I. Pigment Blues 1, 2, 3,15, 15:1, 15:2, 15:3, 15:4, 16, 22, and 60; C. I. Pigment Greens 7 and36; solid solutions of the above-listed pigments; and the like. Thewater-based ink of the present teaching may be a resin-dispersiblepigment ink in which the pigment is dispersed in water with adispersant. As the dispersant, it is allowable to use, for example, anygeneral polymeric dispersant (pigment dispersing resin). Alternatively,the pigment contained in the water-based ink of the present teaching maybe subjected to polymer capsulation.

The pigment may be a self-dispersible pigment. Namely, the water-basedink of the present teaching may be a self-dispersible pigment ink inwhich the self-dispersible pigment is used as the pigment. Theself-dispersible pigment is dispersible in water without using anydispersant, for example, owing to the fact that at least one of thehydrophilic functional group and the salt thereof including, forexample, carbonyl group, hydroxyl group, carboxylic acid group, sulfonicacid group (sulfonate group), and phosphoric acid group (phosphategroup) is introduced into the surfaces of the pigment particles by thechemical bond directly or with any group intervening therebetween. It ispossible to use self-dispersible pigments subjected to the surfacetreatment by any one of methods described, for example, in JapanesePatent Application Laid-open No. HEI8-3498 (corresponding to U.S. Pat.No. 5,609,671), Published Japanese Translation of PCT InternationalPublication for Patent Application No. 2000-513396 (corresponding toU.S. Pat. No. 5,837,045), Published Japanese Translation of PCTInternational Publication for Patent Application No. 2008-524400(corresponding to United States Patent Application Publication No. US2006/0201380), Published Japanese Translation of PCT InternationalPublication for Patent Application No. 2009-515007 (corresponding toUnited States Patent Application Publications No. US 2007/0100023 andNo. US 2007/0100024), and Published Japanese Translation of PCTInternational Publication for Patent Application No. 2011-515535(corresponding to United States Patent Application Publication No. US2009/0229489). It is possible to use, as a material for theself-dispersible pigment, either one of the inorganic pigment and theorganic pigment. Further, a pigment which is suitable for theabove-described treatment includes, for example, carbon black such as“MA8” and “MA100” produced by Mitsubishi Chemical Corporation. As theself-dispersible pigment, it is possible to use, for example, acommercially available product. The commercially available productincludes, for example, “CAB-O-JET (trade name) 200”, “CAB-O-JET (tradename) 250C”, “CAB-O-JET (trade name) 260M”, “CAB-O-JET (trade name)270Y”, “CAB-O-JET (trade name) 300”. “CAB-O-JET (trade name) 400”,“CAB-O-JET (trade name) 450C”, “CAB-O-JET (trade name) 465M” and“CAB-O-JET (trade name) 470Y” produced by Cabot Corporation; “BONJET(trade name) BLACK CW-2” and “BONJET (trade name) BLACK CW-3” producedby Orient Chemical Industries, Ltd.; and “LIOJET (trade name) WD BLACK002C” produced by Toyo Ink SC Holdings Co., Ltd.

The solid content blending amount of the pigment (pigment solid contentamount) in the entire amount of the water-based ink is not particularlylimited, and may be appropriately determined based on desired opticaldensity, color (hue, tint), or the like. The pigment solid contentamount is, for example, in a range of 0.1% by weight to 20% by weight,is preferably in a range of 1% by weight to 15% by weight, and is morepreferably in a range of 2% by weight to 10% by weight.

The water-based ink may or may not contain another colorant such as adye, in addition to the pigment. Note that the effect of the presentteaching is such that the water-based pigment ink using the pigment asthe colorant has a better fixation performance to glossy paper. Thus,the ratio of the pigment in the colorant is preferably in a range of 90%by weight to 100% by weight, more preferably in a range of 98% by weightto 100% by weight.

The water is preferably ion-exchanged water or pure water (purifiedwater). The blending amount of the water in the entire amount of thewater-based ink (the proportion of the water in the water-based ink) is,for example, in a range of 10% by weight to 90% by weight, andpreferably in a range of 40% by weight to 80% by weight. The proportionof the water in the water-based ink may be, for example, a balance ofthe other components.

As described above, the water-based ink further contains at least one ofa water-soluble resin and a water-dispersible resin (hereinafter to bereferred to as “resin” in some cases); and a micelle-forming compoundhaving an alkyl group and an oxyethylene chain.

Examples of the resin include acrylic resin, styrene acrylic resin,urethane resin, polyvinyl alcohol resin, sodium polyacrylate, acrylicacid-maleic acid copolymer salt, styrene-maleic anhydride copolymerresin, vinyl acetate resin, vinyl acetate-acrylate copolymer resin, andvinyl acetate-ethylene copolymer resin. Of the above examples, the resinis preferably the acrylic resin or the styrene acrylic resin. Further,the resin preferably contains an aryl group.

The weight average molecular weight of the resin is preferably 5,000 ormore, more preferably 7,000 or more. When the weight average molecularweight of the resin is 5,000 or more, the water-based ink having abetter fixation performance to glossy paper can be obtained. The reasonthereof is assumed that the resin of which weight average molecularweight is 5,000 or more contributes to fix pigment particles onto theglossy paper. The present teaching, however, is not limited to thisassumption. When the water-soluble resin is used as the resin, theweight average molecular weight of the water-soluble resin is preferably50,000 or less, more preferably 20,000 or less to prevent the increasein viscosity of the water-based ink. When the water-dispersible resin isused as the resin, the average particle size of the water-dispersibleresin is preferably not more than 200 nm, more preferably not more than150 nm to prevent jetting characteristics of the water-based ink frombeing adversely affected. The average particle size of thewater-dispersible resin can be measured as, for example, the arithmeticmean diameter by using a dynamic light scattering type particle diameterdistribution measuring apparatus “LB-550” produced by HORIBA, Ltd.

The resin may be prepared privately or independently, or anycommercially available product may be used for the resin. Examples ofthe commercially available product include “JOHNCRYL (trade name) 537”(acrylic resin), “JOHNCRYL (trade name) 60” (acrylic resin), “JOHNCRYL(trade name) 450” (styrene acrylic resin), “JOHNCRYL (trade name) 390”(acrylic resin), “JOHNCRYL (trade name) 62” (styrene acrylic resin), and“JOHNCRYL (trade name) HPD-96” (styrene acrylic resin) produced by BASFCorporation; “F-52” (acrylic resin), “KE-1148” (acrylic resin), and“PE-1034 (styrene acrylic resin) produced by SEIKO PMC CORPORATION;“SUPERFLEX 210” (urethane resin) and “SUPERFLEX E-4000” (urethane resin,active ingredient amount=45% by weight) produced by DAI-ICHI KOGYOSEIYAKU CO., LTD. “UCOAT (trade name) UWS-145” (urethane resin),“PERMARIN (trade name) UA-150” (urethane resin), and “PERMARIN (tradename) UA-368” (urethane resin) produced by Sanyo Chemical Industries,Ltd.; “PVA-220” (10% aqueous solution of polyvinyl alcohol resin) and“PVA-203” (10% aqueous solution of polyvinyl alcohol resin) produced byKURARAY CO., LTD.; and “AQUALIC (trade name) L DL-40” (sodiumpolyacrylate, active ingredient amount=40% by weight) and “AQUALIC(trade name) L TL-37” (acrylic acid-maleic acid copolymer salt, activeingredient amount=37% by weight) produced by NIPPON SHOKUBAI CO., LTD.In the water-based ink, the resin may be a binder resin or a pigmentdispersing resin.

The acid value of the resin is, for example, not less than 20 mgKOH/g,preferably not less than 100 mgKOH/g. Using the resin of which acidvalue is not less than 100 mgKOH/g results in the water-based ink havinga better fixation performance to glossy paper. The reason thereof isassumed as follows. Namely, the resin having a high acid value, i.e.,having many carboxyl groups has high hydrophilicity, and thus moleculesin the water-based ink are easy to be mutually entangled. This helps toform a film. The present teaching, however, is not limited to thisassumption. Of the above-described commercially available products,“JOHNCRYL (trade name) 60” (acrylic resin), “JOHNCRYL (trade name) 450”(styrene acrylic resin), and the like are examples of the resin of whichacid value is not less than 100 mgKOH/g. The upper limit of the acidvalue of the resin is not particularly limited, and it is, for example,not more than 400 mgKOH/g.

The minimum film-forming temperature of the resin is not more than 80°C., preferably not more than 50° C. Using the resin of which minimumfilm-forming temperature is not more than 50° C. results in thewater-based ink having a better fixation performance to glossy paper. Ofthe above-described commercially available products, “JOHNCRYL (tradename) 537” (acrylic resin) produced by BASF Corporation and the like isan example of the resin of which minimum film-forming temperature is notmore than 50° C. The lower limit of the minimum film-forming temperatureof the resin is not particularly limited, and it is for example, notless than 0° C. The minimum film-forming temperature of each of theabove commercially available products is described as follows: “JOHNCRYL(trade name) 537” (the minimum film-forming temperature: 42° C.), and“JOHNCRYL (trade name) 450” (the minimum film-forming temperature: 5°C.) produced by BASF Corporation. In general, the minimum film-formingtemperature is a temperature required to form a film of thewater-dispersible resin forming emulsion. Meanwhile, the water-solubleresin can form a film even at a low temperature (for example, 0° C.).The water-soluble resin is exemplified, for example, by “JOHNCRYL (tradename) 60” produced by BASF Corporation. In the present description, notonly the water-dispersible resin but also the water-soluble resin whichcan form a film at a low temperature is defined to be included in “theresin of which minimum film-forming temperature is not more than 50°C.”.

In view of the jetting stability, it is preferred that the resin be aresin (water-dispersible resin) forming emulsion which is less likely tothicken in the ink. Such a resin is exemplified, for example, by“JOHNCRYL (trade name) 537” (acrylic resin, average particle size: 70nm), and “JOHNCRYL (trade name) 450” (styrene acrylic resin, averageparticle size: 60 nm) produced by BASF Corporation, of theabove-described commercially available products. In view of thepreservation stability, it is preferred that the resin be thewater-soluble resin. Such a resin is exemplified, for example, by“JOHNCRYL (trade name) 60” (acrylic resin, weight average molecularweight: 8,500) produced by BASF Corporation, of the above-describedcommercially available products.

It is allowable that only one kind of the resin is used singly, or twoor more kinds of the resins are used in combination. The water-based inkmay contain only the water-soluble resin as the resin, or may containonly the water-dispersible resin as the resin. The water-based ink mayboth water-soluble resin and water-dispersible resin as the resin. Thesolid content blending amount of the resin in the entire amount of thewater-based ink is, for example, in a range of 1% by weight to 10% byweight, is preferably in a range of 1.5% by weight to 5% by weight, andis more preferably in a range of 2% by weight to 4% by weight.

The micelle-forming compound is not particularly limited, provided thatthe compound can form micelles in the water-based ink. Themicelle-forming compound is exemplified, for example, by nonionicsurfactants “EMULGEN (trade name) 123P” (polyoxyethylene lauryl ether,cloud point >100° C., HLB value of 16.9), “EMULGEN (trade name) 108”(polyoxyethylene lauryl ether, cloud point of 40° C., HLB value of12.1), “EMULGEN (trade name) 109P” (polyoxyethylene lauryl ether, cloudpoint of 83° C., HLB value of 13.6), “EMULGEN (trade name) 220”(polyoxyethylene cetyl ether, cloud point of 98° C., HLB value of 14.2),“EMULGEN (trade name) 409PV” (polyoxyethylene oleyl ether, cloud pointof 55° C., HLB value of 12.0), “EMULGEN (trade name) 430”(polyoxyethylene oleyl ether, cloud point >100° C., HLB value of 16.2).“EMULGEN (trade name) 102KG” (polyoxyethylene oleyl ether, HLB value of6.3), “EMULGEN (trade name) 103” (polyoxyethylene lauryl ether, HLBvalue of 8.1), “EMULGEN (trade name) 104P” (polyoxyethylene laurylether, HLB value of 9.6). “EMULGEN (trade name) 105” (polyoxyethylenelauryl ether, HLB value of 9.7), “EMULGEN (trade name) 106”(polyoxyethylene lauryl ether. HLB value of 10.5), “EMULGEN (trade name)120” (polyoxyethylene lauryl ether, cloud point of 98° C., HLB value of18.1), “EMULGEN (trade name) 130K” (polyoxyethylene lauryl ether, cloudpoint >100° C., HLB value of 18.1), “EMULGEN (trade name) 147”(polyoxyethylene lauryl ether, cloud point >100° C., HLB value of 16.3),“EMULGEN (trade name) 150” (polyoxyethylene lauryl ether, cloudpoint >100° C., HLB value of 18.4), “EMULGEN (trade name) 210P”(polyoxyethylene cetyl ether, HLB value of 10.7), “EMULGEN (trade name)306P” (polyoxyethylene stearyl ether, HLB value of 9.4), “EMULGEN (tradename) 320P” (polyoxyethylene stearyl ether, cloud point of 91° C., HLBvalue of 13.9), “EMULGEN (trade name) 350” (polyoxyethylene stearylether, cloud point >100° C., HLB value of 17.8), “EMULGEN (trade name)404” (polyoxyethylene oleyl ether, HLB value of 8.8), “EMULGEN (tradename) 408” (polyoxyethylene oleyl ether, HLB value of 10.0), and“EMULGEN (trade name) 420” (polyoxyethylene oleyl ether, cloud point of91° C., HLB value of 13.6) produced by Kao Corporation.

To improve the preservation stability, it is preferred that the HLBvalue of the micelle-forming compound be in a range of 12 to 17. Toimprove the fixation performance to the glossy paper, it is preferredthat the micelle-forming compound have a short oxyethylene chain and asmall HLB value. Specifically, the HLB value of the micelle-formingcompound is preferably in a range of 12 to 15. In this situation, it ispreferred that the number of oxyethylene groups in one molecule of themicelle-forming compound be in a range of 5 to 15. The number ofoxyethylene groups is an average value of all the molecules of themicelle-forming compound in the water-based ink.

Using the micelle-forming compound having a higher cloud point (forexample, one having a cloud point of not less than 90° C.) is preferredbecause it hardly causes separation of the water-based ink and thus itimproves the preservation stability. Using the micelle-forming compoundwhich contains the alkyl group having more carbon atoms is preferredbecause it has high hydrophobicity to enhance the compatibility with theresin, thereby further improving the fixation performance to the glossypaper. Further, in view of forming micelles having a diameter greaterthan a diameter of typical voids of the coating layer of the glossypaper, it is preferred that the alkyl group in the micelle-formingcompound has a larger number of carbon atoms. On the other hand, in viewof jetting characteristics of the water-based ink, it is preferred thatthe micelle diameter be smaller. Thus, it is preferred that the alkylchain in the micelle-forming compound has a smaller number of carbonatoms. Furthermore, since the micelle-forming compound having a lowerviscosity is easy to penetrate a gap in resin particles, it is preferredthat the molecular weight per one molecule of the micelle-formingcompound be smaller. Thus, it is preferred that the alkyl group in themicelle-forming compound has a smaller number of carbon atoms. Thenumber of carbon atoms of the alkyl group of the micelle-formingcompound is not particularly limited. The range satisfying the abovecharacteristics in a balanced manner is, for example, 5 to 30.

The micelle-forming compound is a compound represented by the followingformula (1):R—(OCH₂CH₂)_(n)—OH  (1)

in the formula (1),

R is a straight or branched chain alkyl group having 5 to 30 carbonatoms and n is an integer in a range of 5 to 30.

Preferably, in the formula (1), n is an integer in a range of 5 to 25.More preferably, in the formula (1), R is a straight or branched chainalkyl group having 10 to 20 carbon atoms and n is an integer in a rangeof 5 to 20.

It is allowable that only one kind of the micelle-forming compound isused singly, or two or more kinds of the micelle-forming compounds areused in combination. The blending amount of the micelle-forming compoundin the entire amount of the water-based ink is, for example, in a rangeof 0.5% by weight to 20% by weight, preferably in a range of 1% byweight to 10% by weight, more preferably in a range of 2% by weight to6% by weight, and further preferably in a range of 2% by weight to 4% byweight.

According to the present teaching, adding the resin and themicelle-forming compound to the water-based pigment ink as describedabove can improve the fixation performance to glossy paper. Assumedmechanisms about the improvement of fixation performance of thewater-based ink of the present teaching to glossy paper will beexplained by using examples with reference to FIGS. 1 and 2. Themechanisms, however, are just assumptions and the present teaching isnot limited to those.

FIGS. 1A to 1C each illustrate an exemplary assumed mechanism about theimprovement of the fixation performance of resin-dispersible pigment inkto glossy paper, the resin-dispersible pigment ink being an exemplarywater-based pigment ink. In this example, at least one of thewater-soluble resin having a minimum film-forming temperature of notmore than 80° C. and the water-dispersible resin having a minimumfilm-forming temperature of not more than 80° C. is used as the pigmentdispersing resin. As depicted in FIGS. 1A to 1C, a glossy paper P is,for example, composed of a base paper P1; and a coating layer P2 whichis made of particles 31, such as silica or alumina, covered with abinder resin 32 and which is stacked on a recording side of the basepaper P1. As described above, the average of diameter sizes of typicalvoids of the coating layer P2 of the glossy paper P is in a range ofabout 10 nm to about 50 nm. Meanwhile, the typical average particle sizeof pigment particles 21 is about 100 nm. Thus, as depicted in FIG. 1A,when the water-based ink containing the pigment particles 21 coveredwith a pigment-dispersing resin 22 is discharged or jetted onto theglossy paper P, the pigment particles 21 covered with thepigment-dispersing resin 22 remain or stay on the surface of the glossypaper P without getting through the coating layer P2 of the glossy paperP. If the resin-dispersible pigment ink contains no micelle-formingcompound of the present teaching, the pigment particles 21 covered withthe pigment-dispersing resin 22 and deposited on the glossy paper P cannot form a coating layer having sufficient strength and the coating filmwith insufficient strength is easily peeled off by being rubbed softly.On the other hand, as depicted in FIG. 1B, when the resin-dispersiblepigment ink contains the micelle-forming compound of the presentteaching, the micelle-forming compound forms micelles 23 in thewater-based ink and thus the micelle-forming compound stays or remainson the surface of the glossy paper P without getting through the coatinglayer P2 of the glossy paper P. In particular, micelles 23 of themicelle-forming compound enter between the pigment particles 21 coveredwith the pigment-dispersing resin 22. The micelle-forming compound hasthe hydrophobic alkyl group, and thus it has high compatibility with thepigment-dispersing resin 22. As a result, as depicted in FIG. 1(C), themicelle-forming compound dissolves the pigment-dispersing resin 22 tostrongly connect the pigment particles 21 to each other. Accordingly,the fixation performance of the pigment particles 21 to the glossy paperP improves. It is preferred that the diameter of each micelle of themicelle-forming compound be in a range of about 10 nm to about 200 nm.

FIGS. 2A to 2C each illustrate an exemplary assumed mechanism about theimprovement of the fixation performance of the self-dispersible pigmentink to glossy paper. As depicted in FIG. 2A, in the self-dispersiblepigment ink, self-dispersible pigment particles 21 and resin 22 stay onthe surface of the glossy paper P in a state of being mixed with eachother. If the self-dispersible pigment ink contains no micelle-formingcompound of the present teaching, the self-dispersible pigment particles21 deposited on the glossy paper P can not form a coating layer havingsufficient strength and the coating film with insufficient strength iseasily peeled off by being rubbed softly. On the other hand, when theself-dispersible pigment ink contains the micelle-forming compound ofthe present teaching, three constituents including the self-dispersiblepigment particles 21, the resin 22, and micelles 23 of themicelle-forming compound are mixed with one another on the glossy paperP. As a result, as depicted in FIG. 2C, the micelle-forming compounddissolves the resin 22 to strongly connect the self-dispersible pigmentparticles 21 to each other. Accordingly, the fixation performance to theglossy paper P improves. Except for the above, the assumed mechanism ofthe self-dispersible pigment ink is similar to that of theresin-dispersible pigment ink depicted in FIGS. 1A to 1C.

In order to improve the fixation performance of pigment particles toglossy paper, the ratio (weight ratio) (X/Y) of the blending amount (X:% by weight) of the micelle-forming compound in the water-based ink withrespect to the blending amount (Y: % by weight) of the resin in thewater-based ink is preferably in a range of 0.5 to 3.0, more preferably0.5 to 2.0. Similarly, in order to improve the fixation performance ofpigment particles to glossy paper, the ratio (weight ratio) (X/Z) of theblending amount (X: % by weight) of the micelle-forming compound in thewater-based ink with respect to the blending amount (Z: % by weight) ofthe pigment in the water-based ink is preferably in a range of 0.2 to1.4, more preferably 0.6 to 1.0. The micelle-forming compound is a kindof the surfactant. The surfactant may be contained in the water-basedink to adjust the surface tension of the water-based ink. When thesurfactant is used for such a purpose such as the adjustment of surfacetension of the water-based ink, satisfactory effect can be obtained byusing a small amount of surfactant. As for the water-based ink of thepresent teaching, the micelle-forming compound forming micelles in thewater-based ink is added to improve the fixation performance of pigmentparticles to glossy paper. When the surfactant is used for a purpose ofimproving the fixation performance of pigment particles to glossy paper,the blending amount of the micelle-forming compound in the water-basedink is preferably larger than the case in which the surfactant is usedfor adjustment of surface tension of the water-based ink. Further, theratio (X/Y) of the blending amount (X: % by weight) of themicelle-forming compound in the water-based ink with respect to theblending amount (Y: % by weight) of the resin in the water-based ink andthe ratio (X/Z) of the blending amount (X: % by weight) of themicelle-forming compound in the water-based ink with respect to theblending amount (Z: % by weight) of the pigment in the water-based inkare preferably larger than the case in which the surfactant is used foradjustment of surface tension of the water-based ink.

The water-based ink may further contain a water-soluble organic solvent.The water-soluble organic solvent is exemplified, for example, by ahumectant which prevents the water-based ink from drying at an end of anozzle in an ink-jet head and a penetrant which adjusts the dryingvelocity on a recording medium.

The humectant is not particularly limited, and is exemplified, forexample, by lower alcohols such as methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,and tert-butyl alcohol; amides such as dimethylformamide anddimethylacetamide; ketones such as acetone; ketoalcohols (ketonealcohols) such as diacetone alcohol; ethers such as tetrahydrofuran anddioxane; polyethers such as polyalkylene glycol; polyvalent alcoholssuch as alkylene glycol, glycerol, trimethylolpropane, andtrimethylolethane; 2-pyrrolidone; N-methyl-2-pyrrolidone; and1,3-dimethyl-2-imidazolidinone. The polyalkylene glycol is exemplified,for example, by polyethylene glycol and polypropylene glycol. Thealkylene glycol is exemplified, for example, by ethylene glycol,propylene glycol, butylene glycol, diethylene glycol, triethyleneglycol, dipropylene glycol, tripropylene glycol, thiodiglycol, andhexylene glycol. It is allowable that only one kind of the humectant asdescribed above is used singly, or two or more kinds of the humectantsare used in combination.

The blending amount of the humectant in the entire amount of thewater-based ink is, for example, in a range of 0% by weight to 95% byweight, preferably in a range of 5% by weight to 80% by weight, and morepreferably in a range of 5% by weight to 50% by weight.

The penetrant includes, for example, glycol ether. The glycol ether isexemplified, for example, by ethylene glycol methyl ether, ethyleneglycol ethyl ether, ethylene glycol-n-propyl ether, diethylene glycolmethyl ether, diethylene glycol ethyl ether, diethylene glycol-n-propylether, diethylene glycol-n-butyl ether, diethylene glycol-n-hexyl ether,triethylene glycol methyl ether, triethylene glycol ethyl ether,triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether,propylene glycol methyl ether, propylene glycol ethyl ether, propyleneglycol-n-propyl ether, propylene glycol-n-butyl ether, dipropyleneglycol methyl ether, dipropylene glycol ethyl ether, dipropyleneglycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropyleneglycol methyl ether, tripropylene glycol ethyl ether, tripropyleneglycol-n-propyl ether, and tripropylene glycol-n-butyl ether. One kindof the penetrant may be used singly, or two or more kinds of thepenetrants may be used in combination.

The blending amount of the penetrant in the entire amount of thewater-based ink is, for example, in a range of 0% by weight to 20% byweight, preferably in a range of 0% by weight to 15% by weight, morepreferably in a range of 1% by weight to 4% by weight.

From the viewpoint of improving the fixation performance to glossypaper, it is preferred that the water-based ink contain thewater-soluble organic solvent having a small HLB value, in particular,the water-soluble organic solvent of which HLB value is not more than 8.Examples of the water-soluble organic solvent of which HLB value is notmore than 8 include triethylene glycol-n-butyl ether (HLB value 8.0).The blending amount of the water-soluble organic solvent of which HLBvalue is not more than 8 in the entire amount of the water-based ink is,for example, in a range of 0.5% by weight to 20% by weight, preferablyin a range of 1% by weight to 10% by weight, and more preferably in arange of 2% by weight to 6% by weight. The HLB value can be calculated,for example, by Davies' method.

The water-based ink may further contain a conventionally known additive,as necessary. The additive includes, for example, pH-adjusting agents,viscosity-adjusting agents, surface tension-adjusting agents, andfungicides. The viscosity-adjusting agents include, for example,polyvinyl alcohol, cellulose, and water-soluble resin.

The water-based ink can be prepared, for example, such that the pigment,water, the resin, the micelle-forming compound, and optionally otheradditive component(s) are mixed uniformly or homogeneously by anyconventionally known method, and undissolved matters are removed by afilter or the like.

As described above, according to the present teaching, the fixationperformance to glossy paper can be improved by allowing the water-basedpigment ink to contain the micelle-forming compound and at least one ofthe water-soluble resin and the water-dispersible resin.

Next, the ink cartridge of the present teaching is characterized bybeing an ink cartridge containing a water-based ink for ink-jetrecording; wherein the water-based ink for ink-jet recording is thewater-based ink for ink-jet recording of the present teaching. Forexample, any conventionally known main body (body) of an ink cartridgecan be used for the main body of the ink cartridge of the presentteaching.

Next, according to the present teaching, there is provided a pigmentfixation auxiliary agent which is characterized by containing the resinand the micelle-forming compound and which helps the fixation of thepigment contained in the water-based ink for ink-jet recording to glossypaper. Further, according to the present teaching, there is provided akit including the pigment fixation auxiliary agent and the water-basedink for ink-jet recording which contains the pigment and water. Thepigment fixation auxiliary agent may further contain any other componentor constituent in the water-based ink than the pigment, such as water,the water-soluble organic solvent and the additive.

Next, an explanation will be given about an ink-jet recording apparatusand an ink-jet recording method of the present teaching.

The ink-jet recording apparatus of the present teaching is an ink-jetrecording apparatus characterized by including: an ink accommodatingsection configured to accommodate an ink therein; and an ink dischargemechanism configured to discharge the ink accommodated in the inkaccommodating section; wherein the ink accommodated in the inkaccommodating section is the water-based ink for ink-jet recording ofthe present teaching.

The ink-jet recording method of the present teaching is an ink-jetrecording method characterized by including: performing recording on arecording medium by discharging, to the recording medium, a water-basedink by an ink-jet system; and using the water-based ink for ink-jetrecording of the present teaching, as the water-based ink.

The ink-jet recording method of the present teaching can be practiced,for example, by using the ink-jet recording apparatus of the presentteaching. The recording includes printing a letter (text), printing animage, printing, etc.

FIG. 3 depicts an exemplary configuration of the ink-jet recordingapparatus of the present teaching. As depicted in FIG. 3, an ink-jetrecording apparatus 1 of the present teaching includes four inkcartridges 2, an ink discharge mechanism (ink-jet head) 3, a head unit4, a carriage 5, a driving unit 6, a platen roller 7 and a purge device8 as main constitutive components or parts.

The four ink cartridges 2 contain four colors of water-based inks,respectively, the four colors being yellow, magenta, cyan and black. Atleast one water-based ink among the four color water-based inks is thewater-based ink for ink-jet recording of the present teaching. Theink-jet head 3 disposed on the head unit 4 performs recording on arecording medium (for example, glossy paper) P. The four ink cartridges2 and the head unit 4 are provided or arranged on the carriage 5. Thedriving unit 6 reciprocates the carriage 5 in a linear direction. As thedriving unit 6, it is possible to use, for example, a conventionallyknown driving unit (see, for example, Japanese Patent Applicationlaid-open No. 2008-246821 corresponding to United States PatentApplication Publication No. US2008/0241398). The platen roller 7 extendsin the reciprocating direction of the carriage 5 and is arranged to faceor be opposite to the ink-jet head 3.

The purge device 8 sucks or draws unsatisfactory ink (poor ink) whichcontains air bubbles, etc. accumulated or trapped in the inside of theink-jet head 3. As the purge device 8, it is possible to use, forexample, a conventionally known purge device (for example, see JapanesePatent Application laid-open No. 2008-246821 corresponding to UnitedStates Patent Application Publication No. US2008/0241398).

A wiper member 20 is provided on the purge device 8, at a position onthe side of the platen roller 7 such that the wiper member 20 isadjacent to the purge device 8. The wiper member 20 is formed to have aspatula shape, and wipes a nozzle-formed surface of the ink-jet head 3accompanying with the movement (reciprocating movement) of the carriage5. In FIG. 3, a cap 18 is provided to cover a plurality of nozzles ofthe ink-jet head 3 which is returned to a reset position upon completionof the recording, so as to prevent the water-based inks from drying.

In the ink-jet recording apparatus 1 of this embodiment, the four inkcartridges 2 are provided, together with the head unit 4, on onecarriage 5. However, the present teaching is not limited to this. In theink-jet recording apparatus 1, the respective four cartridges 2 may beprovided on a carriage which is different (separate) from the carriageon which the head unit 4 is provided. Alternatively, the respective fourcartridges 2 may be arranged and fixed inside the ink-jet recordingapparatus 1, rather than being provided on the carriage 5. In suchaspects, for example, each of the four cartridges 2 and the head unit 4which is provided on the carriage 5 are connected with a tube, etc., andthe water-based inks are supplied from the four cartridges 2,respectively, to the head unit 4 via the tubes.

Ink-jet recording using the ink-jet recording apparatus 1 is performed,for example, in the following manner. Namely, at first, the glossy paperP is supplied or fed from a feed cassette (not depicted in the drawing)arranged at a side of or at a position below the ink-jet recordingapparatus 1. The glossy paper P is introduced or guided between theink-jet head 3 and the platen roller 7. Then, a predetermined recordingis performed on the fed or introduced glossy paper P with thewater-based ink(s) discharged or jetted from the ink-jet head 3. Theglossy paper P after the recording is discharged from the ink-jetrecording apparatus 1. According to the present teaching, it is possibleto obtain a recorded matter having a good fixation performance to theglossy paper P. In FIG. 3, the feed mechanism and discharge mechanismfor the glossy paper P are omitted in the drawing.

In the apparatus depicted in FIG. 3, an ink-jet head of serial type(serial type ink-jet head) is adopted. However, the present teaching isnot limited to this. The ink-jet recording apparatus may be an apparatusadopting an ink-jet head of line type (line type ink-jet head).

EXAMPLES

Next, examples of the present teaching will be explained together withcomparative examples. Note that the present teaching is not limited andis not restricted to the examples and the comparative examples whichwill be described below.

Examples 1 to 9 and Comparative Examples 1 and 2

Components, except for a self-dispersible pigment, which were includedin Water-based Ink Composition (TABLE 1) were mixed uniformly orhomogeneously; and thus an ink solvent was obtained. Subsequently, theink solvent was added to the self-dispersible pigment dispersed inwater, followed by being mixed uniformly. After that, the obtainedmixture was filtrated through a cellulose acetate membrane filter (poresize 3.00 μm) produced by Toyo Roshi Kaisha, Ltd., and thus thewater-based ink for ink-jet recording of each of Examples 1 to 9 andComparative Examples 1 and 2 was obtained.

Regarding the water-based inks of Examples 1 to 9 and ComparativeExamples 1 and 2, evaluation of fixation performance to glossy paper wasperformed by the following method.

[Evaluation Method of Fixation Performance to Glossy Paper]

A digital multi-function peripheral equipped with an ink-jet printer“MFC-J4510N” manufactured by BROTHER KOGYO KABUSHIKI KAISHA was used torecord an image including a single color patch on glossy paper (photoglossy paper “BP71GA4”, exclusive or dedicated paper manufactured byBROTHER KOGYO KABUSHIKI KAISHA), with a resolution of 1200 dpi×2400 dpi,by using each of the water-based inks of Examples 1 to 9 and ComparativeExamples 1 and 2. Thus, evaluation samples were produced. Each of theevaluation samples was rubbed with a rubber glove to which a constantload of 8×10³ Pa was applied at predetermined time intervals. Therubbing-off on and around the rubbed part was observed visually inaccordance with the following evaluation criteria. In the followingevaluation criteria, “dirt” means color staining of the water-based inkwhich is caused by the water-based ink spreading over a non-recordedpart of the glossy paper, and “rubbing-off” means a scratch (damagecaused by rubbing) caused in a recorded part of the glossy paper.

<Evaluation Criteria for Evaluation of Fixation Performance to GlossyPaper>

AA: When the evaluation sample was rubbed after the elapse of one minutefrom its manufacture, no dirt and no rubbing-off were caused on andaround the rubbed part.

A: When the evaluation sample was rubbed after the elapse of two minutesfrom its manufacture, no dirt and no rubbing-off were caused on andaround the rubbed part.

A—: When the evaluation sample was rubbed after the elapse of fiveminutes from its manufacture, no dirt and no rubbing-off were caused onand around the rubbed part.

B: When the evaluation sample was rubbed after the elapse of fiveminutes from its manufacture, no dirt was caused but rubbing-off wascaused on and around the rubbed part.

C: When the evaluation sample was rubbed after the elapse of fiveminutes from its manufacture, dirt and rubbing-off were caused on andaround the rubbed part.

TABLE 1 shows the water-based ink compositions and the evaluationresults of the water-based inks of Examples 1 to 9 and ComparativeExamples 1 and 2.

TABLE 1 (Following)—LEGEND

*1: Self-dispersible magenta pigment; produced by Cabot Corporation;numerals in TABLE 1 indicate pigment solid content amounts

*2: Water-dispersible resin (acrylic resin); produced by BASFCorporation; acid value of 40 mgKOH/g; numerals in TABLE 1 indicatesolid content amounts

*3: Water-dispersible resin (acrylic resin); produced by BASFCorporation; acid value of 215 mgKOH/g; numerals in TABLE 1 indicatesolid content amounts

*4: Water-dispersible resin (styrene acrylic resin); produced by BASFCorporation; acid value of 100 mgKOH/g; numerals in TABLE 1 indicatesolid content amounts

*5: Polyoxyethylene (23) lauryl ether; produced by Kao Corporation;cloud point >100° C.; HLB value of 16.9

*6: Polyoxyethylene (6) lauryl ether; produced by Kao Corporation; cloudpoint of 40° C.; HLB value of 12.1

*7: Polyoxyethylene (9) lauryl ether; produced by Kao Corporation; cloudpoint of 83° C.; HLB value of 13.6

*8: Polyoxyethylene (13) cetyl ether; produced by Kao Corporation; cloudpoint of 98° C.; HLB value of 14.2

*9: Polyoxyethylene (9) oleyl ether; produced by Kao Corporation; cloudpoint of 55° C.; HLB value of 12.0

*10: HLB value of 8.0

*11: HLB value of 10.5

TABLE 1 Examples 1 2 3 4 5 6 7 8 9 Water- Pigment Cab-o-jet 4.00 4.004.00 4.00 4.00 4.00 4.00 4.00 6.00 based ink (trade name) 465M (*1)composition Resin JOHNCRYL 3.00 3.00 — — 3.00 3.00 3.00 3.00 — (% byweight) (trade name) 537 (*2) JOHNCRYL — — — 3.00 — — — — 3.00 (tradename) 60 (*3) JOHNCRYL — — 3.00 — — — — — — (trade name) 450 (*4)Micelle- EMULGEN 4.00 4.00 4.00 4.00 — — — — 4.00 forming (trade name)123P (*5) compound EMULGEN — — — — 4.00 — — — — (trade name) 108 (*6)EMULGEN — — — — — 4.00 — — — (trade name) 109P (*7) EMULGEN — — — — — —4.00 — — (trade name) 220 (*8) EMULGEN — — — — — — — 4.00 — (trade name)409PV (*9) Water-soluble Triethylene glycol- 2.00 — 2.00 2.00 2.00 2.002.00 2.00 2.00 organic solvent n-butyl ether (*10) Triethylene glycol(*11) — 2.00 — — — — — — — Humectant 85% glycerol 20.00  20.00  20.00 20.00  20.00  20.00  20.00  20.00  20.00  Water 67.00  67.00  67.00 67.00  67.00  67.00  67.00  67.00  65.00  Fixation performance to glossypaper A A- AA AA AA AA AA AA AA Comparative Examples 1 2 Water- PigmentCab-o-jet (trade name) 465M (*1) 4.00 4.00 based ink Resin JOHNCRYL(trade name) 537 (*2) — 3.00 composition JOHNCRYL (trade name) 60 (*3) —— (% by weight) JOHNCRYL (trade name) 450 (*4) — — Micelle-formingEMULGEN (trade name) 123P (*5) 4.00 — compound EMULGEN (trade name) 108(*6) — — EMULGEN (trade name) 109P (*7) — — EMULGEN (trade name) 220(*8) — — EMULGEN (trade name) 409PV (*9) — — Water-soluble Triethyleneglycol-n-butyl ether (*10) 2.00 2.00 organic solvent Triethylene glycol(*11) — — Humectant 85% glycerol 20.00  20.00  Water 70.00  71.00 Fixation performance to glossy paper C C

As shown in TABLE 1, regarding Examples 1 to 9, the evaluation resultsof fixation performance to glossy paper were good. Especially, regardingeach of Examples 1 and 3 to 9 in which the water-soluble organic solventhaving a HLB value of not more than 8 was used, the evaluation result offixation performance to glossy paper was excellent. Regarding each ofExamples 3, 4 and 9 in which the resin having an acid value of not lessthan 100 mgKOH/g was used and each of Examples 5 to 8 in which themicelle-forming compound having a HLB value of 12 to 15 was used, theevaluation result of fixation performance to glossy paper was extremelyexcellent. Further, regarding each of Examples 1 to 9, the ratio (X/Y)of the blending amount (X: % by weight) of the micelle-forming compoundin the water-based ink with respect to the blending amount (Y: % byweight) of the resin in the water-based ink was in a range of 0.5 to2.0, and the ratio (X/Z) of the blending amount (X: % by weight) of themicelle-forming compound in the water-based ink with respect to theblending amount (Z: % by weight) of the pigment in the water-based inkwas preferably in a range of 0.6 to 1.0.

Regarding Comparative Example 1 in which no resin was used andComparative Example 2 in which no micelle-forming compound was used, theevaluation results of fixation performance to glossy paper were bad.

As described above, the water-based ink of the preset teaching hasexcellent fixation performance to glossy paper. The way of use of thewater-based ink of the present teaching is not particularly limited, andthe water-based ink is widely applicable to various types of ink-jetrecording.

What is claimed is:
 1. A water-based ink for ink-jet recordingcomprising: a pigment; water; a water-soluble resin having a minimumfilm-forming temperature of not more than 80° C., a water-dispersibleresin having a minimum film-forming temperature of not more than 80° C.,or both; and a micelle-forming compound having an alkyl group and anoxyethylene chain; wherein a weight ratio (X/Y) of a blending amount (X)of the micelle-forming compound to a blending amount (Y) of thewater-soluble resin and/or the water-dispersible resin in thewater-based ink is in a range of 0.5 to 2.0; and a weight ratio (X/Z) ofthe blending amount (X) of the micelle-forming compound to a blendingamount (Z) of the pigment in the water-based ink is in a range of 0.2 to1.4.
 2. The water-based ink for ink-jet recording according to claim 1,wherein the water-soluble resin, the water-dispersible resin, or both,has an acid value of not less than 100 mgKOH/g.
 3. The water-based inkfor ink-jet recording according to claim 1, wherein the water-solubleresin, the water-dispersible resin, or both, has a minimum film-formingtemperature of not more than 50° C.
 4. The water-based ink for ink-jetrecording according to claim 1, wherein the water-soluble resin, thewater-dispersible resin, or both, is an acrylic resin or a styreneacrylic resin.
 5. The water-based ink for ink-jet recording according toclaim 1, wherein the water-soluble resin, the water-dispersible resin,or both, is an acrylic resin forming emulsion or a styrene acrylic resinforming emulsion, and the micelle-forming compound is a compoundrepresented by the formula (1):R—(OCH₂CH₂)_(n)—OH  (1) in the formula (1), R is a straight or branchedchain alkyl group having 5 to 30 carbon atoms and n is an integer in arange of 5 to
 30. 6. The water-based ink for ink-jet recording accordingto claim 1, wherein the weight ratio (X/Z) of the blending amount of themicelle-forming compound (X) to the blending amount (Z) of the pigmentin the water-based ink is in a range of 0.6 to 1.0.
 7. The water-basedink for ink-jet recording according to claim 1, wherein themicelle-forming compound has a HLB value in a range of 12 to
 17. 8. Thewater-based ink for ink-jet recording according to claim 7, wherein themicelle-forming compound has a HLB value in a range of 12 to
 15. 9. Thewater-based ink for ink-jet recording according to claim 1, furthercomprising a water-soluble organic solvent having a HLB value of notmore than
 8. 10. The water-based ink for ink-jet recording according toclaim 9, wherein the water-soluble organic solvent is triethyleneglycol-n-butyl ether.
 11. The water-based ink for ink-jet recordingaccording to claim 1, wherein the water-soluble resin, thewater-dispersible resin, or both, is a water-dispersible resin formingemulsion.
 12. The water-based ink for ink-jet recording according toclaim 11, wherein the water-dispersible resin forming the emulsion hasan average particle size of not more than 200 nm.
 13. The water-basedink for ink-jet recording according to claim 1, wherein themicelle-forming compound is a compound represented by the formula (1):R—(OCH₂CH₂)_(n)—OH  (1) in the formula (1), R is a straight or branchedchain alkyl group having 5 to 30 carbon atoms and n is an integer in arange of 5 to
 30. 14. The water-based ink for ink-jet recordingaccording to claim 13, wherein the micelle-forming compound is thecompound represented by the formula (1), in the formula (1), R is astraight or branched chain alkyl group having 10 to 20 carbon atoms andn is an integer in a range of 5 to
 20. 15. An ink cartridge whichcomprises the water-based ink for ink-jet recording as defined inclaim
 1. 16. An ink-jet recording method comprising discharging awater-based ink for ink-jet recording on a glossy paper in accordancewith an ink-jet system to perform recording, wherein the water-based inkfor ink-jet recording is the water-based ink for ink-jet recording asdefined in claim 1.